Abstract
The use of pulse-compression in ultrasonic non-destructive testing has assured, in various applications, a significant improvement in the signal-to-noise ratio. In this work, the technique is combined with linear phased array to improve the sensitivity and resolution in the ultrasonic imaging of highly attenuating and scattering materials. A series of tests were conducted on a 60 mm thick carbon fiber reinforced polymer benchmark sample with known defects using a custom-made pulse-compression-based phased array system. Sector scan and total focusing method images of the sample were obtained with the developed system and were compared with those reconstructed by using a commercial pulse-echo phased array system. While an almost identical sensitivity was found in the near field, the pulse-compression-based system surpassed the standard one in the far-field producing a more accurate imaging of the deepest defects and of the backwall of the sample.
Highlights
Dipartimento di Ingegneria Informatica, Modellistica, Elettronica e Sistemistica, Università della Calabria, Abstract: The use of pulse-compression in ultrasonic non-destructive testing has assured, in various applications, a significant improvement in the signal-to-noise ratio
Ultrasonic images with even better spatial resolution and signal-to-noise ratio (SNR) can be obtained by post-processing techniques such as full matrix capture (FMC), where each transmitting element is fired alone, and the responses of all the receiving elements are collected and stored
Examples of the signals involved in the pulse ultrasonic measurement: the input applied to the transmitting element; the echo signal acquired through the reception element of the array applied to the transmitting element; the echo signal acquired through the reception element of the array transducer transducer; the impulse response of the sample under test (SUT) retrieved by convolving the acquired signal; the impulse response of the sample under test (SUT) retrieved by convolving the acquired signal with the with the matched filter
Summary
Ultrasonic testing (UT) is the most widespread non-destructive testing (NDT) technique for the assessment of the structural integrity of highly attenuating and scattering materials, such as carbon fiber reinforced polymers (CFRP), both during manufacturing and in service [1,2]. Ultrasonic images with even better spatial resolution and SNR can be obtained by post-processing techniques such as full matrix capture (FMC), where each transmitting element is fired alone, and the responses of all the receiving elements are collected and stored. Starting from these data, the total focusing method (TFM) is used to generate 2D or 3D images [13,14]: for the pixels of the image, a specific delay is calculated and applied to all the possible pairs of transmitting and receiving elements and the signals from all the pairs are summed to calculate the pixel intensity.
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